Effect of Heat Treatment on Mechanical Properties of a Novel Ti-6Al-2Mo-2V-3Nb-2Fe-1Zr Alloy
Herein,the effect of heat treatments(solution,solution+single aging and solution+double aging)on the microstructure and mechanical properties of a novel Ti-based alloy Ti-6Al-2Mo-2V-3Nb-2Fe-1Zr was investigated through microstructure characterization and tensile testing.The microstructure ob-servations indicate that the alloy prior to heat treatment possesses a bimodal microstructure consisted of primary αp phase,secondary αs phase,and β phase,and the volume fraction of the primary αp phase and secondary αs phase is 22％and 21％,respectively.After solution treated in the dual phase zone,a portion of the original αp and αs phases was replaced by β phase and the alloy microstructure is comprised of metastable β phase,equiaxed primary αp phase,and coarse lamellar secondary αs phase.After single ag-ing,a large number of evenly distributed needle-like nano secondary αs phases are precipitated within theβ phase;After double aging,the volume fraction of α phase increases significantly,while the grain size of primary αp phase and secondary αs phase increases with the increasing aging time.Quasi-static tensile test results reveal that alloys subjected to solution treatment in the dual phase zone exhibit significant en-hancements in elongation compared to the as hot-rolled ones,but yielding at lower stress levels.Single aging results in significant increase of strength,thereby presenting an improved strength-ductility balance of the alloy.In comparison with the hot rolling process,the double aging process is unfavored to the duc-tility,moreover,with the increasing aging time,the strength decreases and elongation increases gradual-ly.Finally,the variation in the work hardening rate of the alloy subjected to different heat treatments may be explained by work hardening rate-strain curves.Based on the experimental data,the modified Hall-Petch constitutive model is fitted,whilst the results predicted by this constitutive model have high coinci-dence with the experimental data.
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